US8773796B2 - System and method of synchronized writing on bit patterned media with read-write offset - Google Patents
System and method of synchronized writing on bit patterned media with read-write offset Download PDFInfo
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- US8773796B2 US8773796B2 US13/204,360 US201113204360A US8773796B2 US 8773796 B2 US8773796 B2 US 8773796B2 US 201113204360 A US201113204360 A US 201113204360A US 8773796 B2 US8773796 B2 US 8773796B2
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- 238000000034 method Methods 0.000 title claims abstract description 38
- 230000001360 synchronised effect Effects 0.000 title description 2
- 230000008901 benefit Effects 0.000 description 9
- 230000000694 effects Effects 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000004422 calculation algorithm Methods 0.000 description 1
- 230000005055 memory storage Effects 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
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Classifications
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
- G11B5/58—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
- G11B5/596—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for track following on disks
- G11B5/59605—Circuits
- G11B5/59616—Synchronisation; Clocking
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
- G11B20/10—Digital recording or reproducing
- G11B20/10009—Improvement or modification of read or write signals
- G11B20/10222—Improvement or modification of read or write signals clock-related aspects, e.g. phase or frequency adjustment or bit synchronisation
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
- G11B20/10—Digital recording or reproducing
- G11B20/10009—Improvement or modification of read or write signals
- G11B20/10305—Improvement or modification of read or write signals signal quality assessment
- G11B20/10398—Improvement or modification of read or write signals signal quality assessment jitter, timing deviations or phase and frequency errors
- G11B20/10435—Improvement or modification of read or write signals signal quality assessment jitter, timing deviations or phase and frequency errors by verifying the timing of predetermined signal patterns, e.g. sync patterns
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/74—Record carriers characterised by the form, e.g. sheet shaped to wrap around a drum
- G11B5/743—Patterned record carriers, wherein the magnetic recording layer is patterned into magnetic isolated data islands, e.g. discrete tracks
- G11B5/746—Bit Patterned record carriers, wherein each magnetic isolated data island corresponds to a bit
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B2220/00—Record carriers by type
- G11B2220/20—Disc-shaped record carriers
- G11B2220/25—Disc-shaped record carriers characterised in that the disc is based on a specific recording technology
- G11B2220/2508—Magnetic discs
- G11B2220/252—Patterned or quantised magnetic media, i.e. bits are stored in predefined single domain elements
Definitions
- the present invention relates in general to disk drives and, in particular, to a system, method and apparatus for synchronizing writing on bit patterned media.
- the read head provides a timing reference using the patterns on the servoing track. Due to the nature of the pattern generation process between the inner and outer diameters of the disk, the regularity of the patterns is not consistent over the range of the read-write offset. This creates a problem for synchronizing the write signal with the patterns on the write track.
- a method for synchronizing writing in a disk drive may comprise providing the disk drive with a disk having bit patterned media, and a slider with a read head and a write head for reading data from and writing data to the disk, respectively.
- the method may further comprise positioning the read head at a read-write offset with respect to the write head; writing data with the write head onto a data pattern on a write track of the bit patterned media; providing a timing offset between the data pattern on the write track and a data pattern on a servoing track of the bit patterned media with the read head using the data pattern on the servoing track; storing the timing offset in a plurality of sync fields in a plurality of servo sectors on the servoing track; reading back the timing offset stored in the sync fields with the read head; and synchronizing a write signal of the data pattern on the write track with the timing offset read back from the sync fields.
- FIG. 1 is schematic plan view of an embodiment of a disk drive
- FIG. 2 is an enlarged schematic view of an embodiment of a portion of a disk and slider in a disk drive during operation
- FIG. 3 is an enlarged schematic view of an embodiment of another portion of a disk in a disk drive.
- FIG. 1 depicts a hard disk drive assembly 100 comprising a housing or enclosure 101 with one or more media disks 111 rotatably mounted thereto.
- the disk 111 comprises magnetic recording media rotated at high speeds by a spindle motor (not shown) during operation.
- Concentric magnetic data tracks 113 are formed on either or both of the disk surfaces to receive and store information.
- Embodiments of a read/write slider 110 may be moved across the disk surface by an actuator assembly 106 , allowing the slider 110 to read and/or write magnetic data to a particular track 113 .
- the actuator assembly 106 may pivot on a pivot 114 .
- the actuator assembly 106 may form part of a closed loop feedback system, known as servo control, which dynamically positions the read/write slider 110 to compensate for thermal expansion of the magnetic recording media 111 as well as vibrations and other disturbances or irregularities.
- a complex computational algorithm executed by a microprocessor, digital signal processor, or analog signal processor 116 that receives data address information from a computer, converts it to a location on the disk 111 , and moves the read/write slider 110 accordingly.
- read/write heads 110 periodically reference servo patterns recorded on the disk to ensure accurate slider 110 positioning. Servo patterns may be used to ensure a read/write slider 110 follows a particular track 113 accurately, and to control and monitor transition of the slider 110 from one track to another. Upon referencing a servo pattern, the read/write slider 110 obtains head position information that enables the control circuitry 116 to subsequently realign the slider 110 to correct any detected error.
- Servo patterns or servo sectors may be contained in engineered servo sections 112 that are embedded within a plurality of data tracks 113 to allow frequent sampling of the servo patterns for improved disk drive performance, in some embodiments.
- embedded servo sections 112 may extend substantially radially from the center of the magnetic recording media 111 , like spokes from the center of a wheel. Unlike spokes however, servo sections 112 form a subtle, arc-shaped path calibrated to substantially match the range of motion of the read/write slider 110 .
- a method for synchronizing writing in a disk drive comprises providing the disk drive with a disk having bit patterned media, and the slider 110 with a read head 131 ( FIG. 2 ) and a write head 133 for reading data from and writing data to the disk, respectively.
- the method further comprises positioning the read head 131 at a read-write offset 134 with respect to the write head 133 ; writing data with the write head 133 onto a data pattern on a write track 135 of the bit patterned media (the read-write offset 134 may be on the order of, e.g., a few micrometers).
- the method further comprises providing a timing offset 139 between the data pattern on the write track 135 and a data pattern on a servoing track 137 of the bit patterned media with the read head 131 using the data pattern on the servoing track 137 .
- the timing offset may comprise differences in frequency and phase.
- the method may further comprise storing the timing offset 139 in a plurality of sync fields 141 ( FIG. 3 ) in a plurality of servo sectors 143 on the servoing track; reading back the timing offset 139 stored in the sync fields 141 with the read head 131 ; and synchronizing a write signal of the data pattern on the write track 135 with the timing offset 139 read back from the sync fields 141 . These steps may be performed directly from the sync fields without memory storage.
- the method may further comprise adjusting a frequency and phase of a clock of the disk drive with the timing offset stored in the sync fields.
- the method further comprise initially adjusting a clock of the disk drive to synchronize the write signal to a timing of the data pattern on the servoing track, since the slider is skewed relative to the bit patterned media.
- the sync fields 141 may be radially positioned with about half-track offsets in circumferentially alternating servo sectors (e.g., in even numbered and odd numbered sectors) to accommodate varying read-write offsets. This allows the timing offset stored in the sync fields to still be read back by the reader that is not positioned at the center of the servoing track, while the writer is positioned at the center of the write track.
- the read-write offsets vary with the skewed head due to geometric parameters and radial location of the head relative to the disk.
- the reader can read back the data stored on the track when the reader is positioned within +/ ⁇ 50% track pitch of the track center.
- the effective read-write offset is usually not an integer-multiple of the track pitch.
- the effective read-write offset changes with the skew angle.
- the reader is probably not centered on the servoing track.
- the method comprises measuring an optimal timing offset by writing at different timing offsets, each incremented by a step between the servo sectors.
- the optimal timing offset may be determined by reading back the written data and measuring bit error rates in the written data, such that the timing offset corresponding to the smallest bit error rate is the optimal timing offset.
- Each servo sector may contain one sync field, and then store the optimal timing offset between the servoing track and the write track of the sync field as described herein.
- the optimal timing offset may be written in the plurality of sync fields on the plurality of servo sectors in a plurality of servoing tracks.
- Embodiments of a disk drive may comprise a disk having bit patterned media, and a slider with a read head and a write head for reading data from and writing data to the disk, respectively; the read head is spaced part from the write head at a read-write offset; a data pattern on a write track of the bit patterned media; a data pattern on a servoing track of the bit patterned media; a timing offset between the data pattern on the write track and the data pattern on the servoing track; a plurality of sync fields in a plurality of servo sectors on the servoing track for storing the timing offset; and a write signal of the data pattern on the write track is synchronized with the timing of the data pattern on the servoing track, adjusted by the timing offset read back from the sync fields.
- Advantages include storing phase differences in a field inside the servo sector on the read track.
- Each servo sector can potentially have a different optimal write phase correction.
- no look-up tables are used as the optimal write phase for each servo sector is stored in a field inside that servo sector.
- the reference timing may be generated by data islands on the read track.
- the sync fields may be radially offset by half of a track in alternating servo sectors to accommodate variation in read-write offset and changing skew angle of the slider relative to the tracks.
- the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having” or any other variation thereof, are intended to cover a non-exclusive inclusion.
- a process, method, article, or apparatus that comprises a list of features is not necessarily limited only to those features but may include other features not expressly listed or inherent to such process, method, article, or apparatus.
- “or” refers to an inclusive-or and not to an exclusive-or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).
Abstract
Description
Claims (17)
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
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US13/204,360 US8773796B2 (en) | 2011-08-05 | 2011-08-05 | System and method of synchronized writing on bit patterned media with read-write offset |
JP2012172597A JP2013037756A (en) | 2011-08-05 | 2012-08-03 | System and method for synchronous writing on bit pattern medium having reading and writing offset |
Applications Claiming Priority (1)
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US13/204,360 US8773796B2 (en) | 2011-08-05 | 2011-08-05 | System and method of synchronized writing on bit patterned media with read-write offset |
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US20130033777A1 US20130033777A1 (en) | 2013-02-07 |
US8773796B2 true US8773796B2 (en) | 2014-07-08 |
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US13/204,360 Active 2032-05-31 US8773796B2 (en) | 2011-08-05 | 2011-08-05 | System and method of synchronized writing on bit patterned media with read-write offset |
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Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US9818438B1 (en) | 2016-09-30 | 2017-11-14 | Seagate Technology Llc | Skew compensation in a patterned medium |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US8605379B1 (en) * | 2012-09-19 | 2013-12-10 | Western Digital Technologies, Inc. | Disk drive averaging phase-offset due to reader/writer gap in order to recover extended servo data |
Citations (15)
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US6738207B1 (en) | 1999-08-18 | 2004-05-18 | Seagate Technology Llc | Method for synchronizing the write current for magnetic recording with the bit islands on discrete bit patterned media |
JP2004199806A (en) | 2002-12-19 | 2004-07-15 | Toshiba Corp | Recording and reproducing device |
US20060119965A1 (en) | 2004-12-03 | 2006-06-08 | Hitachi Global Storage Technologies Netherlands B.V. | Information recording device using patterned medium and control method thereof |
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US20100073801A1 (en) | 2008-09-22 | 2010-03-25 | Fujitsu Limited | Magnetic recording device, control device, and magnetic recording device control method |
US20100142076A1 (en) | 2008-12-10 | 2010-06-10 | Hitachi Global Storage Technologies Netherlands B.V. | Patterned-media magnetic recording disk with cryptographically scrambled patterns and disk drive operable with the disk |
US20100142077A1 (en) | 2008-12-10 | 2010-06-10 | Hideki Zaitsu | Magnetic recording/reproducing using a patterned medium |
US20100202079A1 (en) | 2009-02-10 | 2010-08-12 | Bruce Douglas Buch | Write synchronization phase calibration for storage media |
US20100238578A1 (en) | 2009-03-19 | 2010-09-23 | Toshiba Storage Device Corporation | Method for generating write clock signal in magnetic disk drive |
US20100238577A1 (en) | 2009-03-18 | 2010-09-23 | Toshiba Storage Device Corporation | Method and apparatus for measuring phase shift in a disk drive having bit-patterned media |
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2011
- 2011-08-05 US US13/204,360 patent/US8773796B2/en active Active
-
2012
- 2012-08-03 JP JP2012172597A patent/JP2013037756A/en active Pending
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Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
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US9818438B1 (en) | 2016-09-30 | 2017-11-14 | Seagate Technology Llc | Skew compensation in a patterned medium |
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JP2013037756A (en) | 2013-02-21 |
US20130033777A1 (en) | 2013-02-07 |
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